1. Field of the Art
This invention relates to an insertion instrument of an endoscope for medical use, and more particularly to a joint construction for connecting an angle section to a flexible body section of an endoscopic insertion instrument.
2. Prior Art
Generally, endoscopes which are in use in medical fields have a construction as shown in FIG. 8. In that figure, indicated at 1 is a manipulating head assembly, at 2 an insertion instrument and at 3 a universal cable of an endoscope. A major part of the insertion instrument 2 consists of an elongated flexible body 2a which is extended out from the manipulating head assembly 1. Connected successively to the fore end of the flexible body 2a are an angle section 2b and a rigid tip end section 2c which is provided with an observation window in its housing along with illumination windows. The angle section 2b is interposed for the purpose of turning the rigid tip end section 2c into aimed directions. The elongated flexible body 2a is arranged to have a flexible structure which is bendable in arbitrary directions along a path of insertion.
Illustrated in FIG. 9 is a joint portion through which the angle section 2b is connected to the flexible elongated body 2a of the insertion instrument 2. Generally, the flexible body 2a, which is required to have flexibility in bending directions, is internally provided with a coil tube as a flexible spinal structure, which is formed by helically winding metal strips of a predetermined width. The coil tube 10 is normally in the form of a double coil tube consisting of two metal coils which are wound in different directions and overlapped one on the other. A mesh layer 11 and an outer skin layer 12 are successively wrapped on and around the coil tube 10 of the flexible body 2a. 
The angle section 2b is arranged to be bent into an angular direction by remote control from an angle knob 4 which is provided on the manipulating head assembly 1. The angle section 2b has a flexible structure which is constituted by a series of flexibly connected angle rings 13. Adjacent angle rings 13 are pivotally connected with each other by a pair of pivoting pins 14 which are located at 180 degrees positions relative to each other. Therefore, the angle rings 13 can be turned about the pivoting pins 14 in a direction perpendicular to the axes of the pivoting pins 14. The angle rings 13 are successively connected by the paired pivoting pins 14 the positions of which are shifted alternately by 90 degrees, so that the angle section 2b can be turned vertically in upward and downward directions and at the same time laterally in rightward and leftward directions. Similarly to the flexible body portion 2a, a mesh layer 15 and an outer skin layer 16 are successively wrapped on the pivotally connected angle rings 13.
The flexible body 2a and the angle section 2b of the insertion instrument are different from each other in construction, so that it is the usual practice to fabricate these parts separately and join them together in a later stage. For the purpose of joining the flexible body 2a and the angle section 2b together, connector rings 17 and 18 are attached to the fore end of the flexible body 2a and the proximal end of the angle section 2b, respectively. After being fitted one on the other, the connector rings 17 and 18 are securely fixed with each other. Indicated at 17 is the connector ring on the side of the flexible body 2a. This connector ring 17 is securely fixed to a fore end of the coil tube 10 of the flexible body 2a by spot welding or by other fixation means. On the other hand, indicated at 18 is the connector ring on the side of the angle section 2b. This connector ring 18 is inserted into a rearmost angle ring 13 and likewise securely fixed to the latter by spot welding or by other suitable fixation means. Part of the connector ring 18 on the side of the angle section 2b is fitted into the connector ring 17 on the side of the flexible body 2a. The connector ring 17 which is fitted on the outer periphery of the connector ring 18 is provided with a plural number of perforations 19. Solder is poured into these perforations 19 to fix the outer connector ring 17 to the inner connector ring 18. The outer skin layers 12 and 16 of the flexible body 2a and the angle section 2b are extended to meet on the outer connector ring, and their meeting ends are fixed in position by line wrapping or by the use of an adhesive.
Fitted in or threaded through the endoscopic insertion instrument 2 are various component parts, including a light guide consisting of a bundle of fiber optics for transmission of illumination light, a signal cable in the case of an electronic endoscope (or an image guide consisting of a bundle of fiber optics in the case of an optical endoscope), a biopsy channel for insertion of a biopsy or surgical instrument or the like, and an air/water feed channel. Further, operating wires 21 are threaded internally of the insertion instrument 2 for angularly bending the angle section 2b by remote control. The operating wires 21 include a pair of operating wires which are so arranged and connected as to turn the angle section 2b angularly in upward and downward directions, and another pair of operating wires which are so arranged and connected as to turn the angle section 2b angularly in lateral direction, that is to say, in rightward and leftward directions. The fore ends of these operating wires 21 are securely fixed either to a foremost angle ring of the angle section 2b or to the rigid tip end section 2c. Within the angle section 2b, the operating wires 21 are threaded through the pivoting pins 14 of the angle rings 13 (or through lancing arches which are provided on the angle rings 13). Further a flexible guide tube in the form of a tightly closed coil tube 22 is fitted in the elongated flexible body 2a, and the above-mentioned operating wires 21 are passed through this tightly closed coil 22. The fore end of the tightly closed coil 22 is fixed to a joint portion of the flexible body 2a with the angle section 2b. 
Illustrated in FIG. 10 is the construction of a fore end portion of the flexible body 2a where the fore end portion of the tightly closed coil 22 is fixed in position. As clear therefrom, by caulking, anchor pins 23 are planted as anchor members in the connector ring 18 on the side of the angle section 2b. A wire passage hole 24 is formed in a head portion 23a of each anchor pin 23, which is located on the inner side of the connector ring 18. Fixedly fitted in the wire passage hole 24 is a pipe member 25 to which the fore end of the tightly closed coil 22 is securely fixed. The fixed pipe member 25 is of a stepped shape having a large diameter portion 25a and a small diameter portion 25b. The fore end of the tightly closed coil 22 is inserted into and securely fixed by soldering to the large diameter portion 25a of the fixed pipe member 25, which is located on the side of the flexible body 2a. The small diameter portion 25b is fitted in the wire passage hole 24, and one operating wire 21 alone is passed through the small diameter portion 25b. 
As described above, various component parts are fitted in or threaded internally of the endoscopic insertion instrument 2. Nevertheless, in the event of a trouble with one of the fitted or threaded component parts, namely, in case any one of the fitted component parts is damaged or deformed, it becomes necessary to inspect the interior parts of the insertion instrument and to replace a damaged or deformed part if any. Besides, it may also become necessary to separate the angle section from the flexible body at the time of inspection or troubleshooting. On such an occasion, it has been the usual practice to remove the solder which fixes the connector rings 17 and 18 together. However, the removal of the solder requires not only a special tool but also meticulous skills. In addition, the removal of the solder could result in deformation of or damage to the fixed pipe member 25.
In joining the connector rings 17 and 18 fixedly to each other, the use of solder itself involves a problem that the joint strength varies from one insertion instrument to another. In addition, in order to distribute solder in the gap space between the two connector rings 17 and 18, it is the usual practice to fill a flux into the perforations 19 beforehand. The applied flux, however, may intrude into interior portions of the insertion instrument and contribute to corrosion of the operating wires 21 of the angle section 2b. 
In order to avoid the above problems or difficulties, it has also been known in the art to fixedly join the angle section and the flexible body of the insertion instrument by means of screw threads. However, since the angle section 2b is turned and twisted during angling operations, various forces are repeatedly exerted on the joint portion between the angle section and the flexible body of the insertion instrument from different directions, resulting in loosening of the screw threads which join together the angle section and the flexible body.
In view of the foregoing situations, it is an object of the present invention to provide a joint construction for connecting an angle section to an elongated flexible body of an endoscopic insertion instrument, which can fix the angle section and flexible body firmly with each other in a stable state, while permitting to separate the angle section from the flexible body easily whenever necessary for inspection or for troubleshooting of an internally fitted component part of the insertion instrument.
It is another object of the present invention to provide a joint construction of the sort as mentioned above, which can join an angle section firmly to the elongated flexible body of the insertion instrument without using solder or similar means.
It is still another object of the present invention to provide a joint construction of the sort as mentioned above, which can join the angle section securely with the flexible body of the insertion instrument by the use of screw threads and in such a manner as to prevent loosening of the screw threads.
In accordance with the present invention, for achieving the above-stated objective, there is provided a joint construction for joining an angle section to an elongated flexible body of an endoscopic insertion instrument, which comprises: a connector ring provided at a proximal end of the angle section; a connector ring provided at a fore end of the flexible body and adapted to be connected with the connector ring on the side of the angle section by fitting engagement, with one connector ring on the outer side of the other connector ring; a number of radially inwardly projecting ridge portions provided at angular intervals on an inner periphery of an inner one of the connector rings; screw holes bored in the inner connector ring radially through the inwardly projecting ridge portions; perforations bored in an outer one of the connector rings in radially aligned positions with respect to the screw holes in the inner connector ring; screw members threaded into the screw holes in the inner connector ring through the perforations in the outer connector ring, each one of the screw members having a head portion of a diameter substantially same as that of the perforations; and a screw anchor ring slidably fitted on the outer connector ring for displacement between a covering position to close in at least part of the head portions of the screw members and an uncovering position to totally expose the head portions of the screw members.
Preferably, the inwardly projecting ridge portions are formed in a convex shape in section. The inwardly projecting ridge portions are also adapted to function as guide ways for operating wires which are threaded through the insertion instrument for angularly bending the angle section. For this purpose, wire passage holes are bored axially through the inwardly projecting ridge portions and in such positions as to evade the screw holes, the wire passage holes being in a stepped shape having a large diameter portion on the side of the flexible body and a small diameter portion on the side of the angle section. The operating wires are threaded through the wire passage holes and connected to the angle section, and flexible coils which sheath the operating wires in the flexible body of the insertion instrument have the respective fore ends thereof securely fixed in the large diameter portions of the wire passage holes.
Further, preferably the inwardly projecting ridge portion is provided in four positions approximately at angular intervals of 90 degrees around the inner periphery of the inner connector ring, and the screw holes are formed at least in two of the inwardly projecting ridges to ensure sufficient joint strength between the angle section and the flexible body. In a case where the connector ring on the side of the angle section is fitted on the inner side of the connector ring on the side of the flexible body, a rearmost one of angle rings of the angle section can be used as the connector ring.
In a preferred form of the invention, the screw anchor ring is axially movable on and along the outer connector ring between a covering position to close on the head portions of the screw members and an uncovering position to totally expose the head portions of the screw members. In another preferred form of the invention, the screw anchor ring is provided with openings larger in diameter than the head portions of the screw members, and adapted to be movable in circumferential direction around outer periphery of the outer connector ring to and from a covering position to close on the head portions of the screw members and an uncovering position to expose the head portions of the screw members through the openings.
The above and other objects, features and advantages of the present invention will become apparent from the following particular description of preferred embodiments, taken in conjunction with the accompanying drawings which show by way of example some preferred embodiments of the invention. Needless to say, the present invention should not be construed as being limited to the particular forms shown in the drawings.